Synthesis rates of cellular proteins involved in translation and protein folding are strongly altered in response to overproduction of basic fibroblast growth factor by recombinant Escherichia coli.

The cellular response to temperature-induced production of human basic fibroblast growth (bFGF) factor by recombinant E. coli (bacteriophage lambda PRPL promoter/cI857 repressor expression system) was studied by one- and two-dimensional gel electrophoresis. Temperature shift from 30 to 42 degrees C caused the induction of heat-shock protein synthesis and the repression of synthesis of ribosomal proteins and the protein folding catalyst trigger factor. Compared to control cells, carrying the expression vector without structural bFGF gene cells, producing the heterologous protein exhibited a stronger increase in the synthesis rate of heat-shock proteins ClpB (HtpM), DnaK, HtpG, GroEL, GrpE, and IbpB (HtpE) in response to temperature upshift. Unexpectedly, formation of the chaperone heat-shock protein GroES was not detected after temperature shift to 42 degrees C in cells producing bFGF. In addition to amplified heat-shock protein formation, the syntheses of ribosomal proteins and of the protein folding catalyst trigger factor were more severely repressed after temperature upshift in cells producing bFGF. In conclusion, the normal cellular stress response caused by the high inducing temperature was strongly amplified by heterologous protein synthesis. In particular, syntheses of proteins involved in translation and protein folding were affected by the overproduction of the heterologous protein.